Hematopoietic stem-cell transplants (HSCT) are commonly used in the treatment of blood and lymphoid cancers. In an allogeneic transplant, the transplanted cells come from a donor. After an allogeneic HSCT, patients typically take more than a dozen medications to prevent rejection of the transplanted cells and to fend off infections. This medication regimen is both complex and requires rigorous adherence, usually extending for at least 6 months after transplantation. Clinical data suggest that medication non-adherence places patients at risk for increased morbidity and mortality, requiring hospital readmissions that lead to increased personal and healthcare costs. No systematic studies are available on HSCT patients' medication adherence after transplant, despite the fact that non-adherence can have severe consequences. Therefore, predictors of non-adherence in HSCT patients are poorly understood. Theoretical models of adherence and research with solid organ transplant patients delineate possible risk factors, such as having a history of non-adherence, lack of social support, and depression. These factors are more prevalent among low-income and ethnic minority patients for whom post-transplant mortality and morbidity are higher in comparison to majority groups. In sum, there is clearly a need to study (1) medication adherence in allogeneic HSCT patients, (2) the link between adherence and transplant outcomes, and (3) predictors of HSCT patients' adherence, including the effects of low-income and minority status. To address this scientific need, the study will assess medication adherence in 60 allogeneic HSCT patients, including 30 minority patients, during the first six months post treatment. In addition, the study will use a multi- method approach to examine adherence predictors and strategies qualitative patient interviews and standard questionnaires. The proposed research is innovative in three distinct ways: 1) it will address the understudied problem of medication adherence in HSCT patients; 2) it will use daily electronic monitoring, drug plasma levels, and self-report to assess adherence with a complex medication regimen; and 3) it will apply an established empirically supported theory of adherence model (the Information-Motivation-Behavioral Skills Model) to this population. We anticipate that the proposed study will identify strategies to promote adherence in patients with complex medication regimens who are at risk for non-adherence, including minority patients.